Blades for gas turbine engines



Sept. 12, 1961 G. o. ECCLES BLADES FOR GAS TURBINE ENGINES Filed May a,1959 Ill llllllllll I Iv EQM l llllllllll I I I I l I I l l l l l l l lI I I I I I I llullll-l |llll-\l l-Illlllllll-lw FIG.2.

llllllllllll INVENTOR 605? o-smo Ccc AT TORNEYS Filed May 8, 1959, Ser.No. 811,831 Claims priority, application Great Britain May 21, 1958 3Claims. (Cl. 29-4563} The invention relates to a method of formingplatforms, shrouds and the like on blades for gas turbine engines.

The invention is applicable to blades which have passages for cooling orheating fiuid running axially through them.

It has been found in practice that when a blank is formed with suchaxial passages or holes running through it and a laterally extendedportion subsequently formed at one end of the blank by upsetting orforging to form a tip platform or shroud the holes in the area of theplatform or shroud tend to bend that is to be deflected from the axialdirection.

According to the invention the method of forming the shroud or tipplatform portion includes further shaping of the laterally extendedportion in a die'having a cavity in it beyond the end of the blade intowhich some of the metal of the blank is caused to how, drawing out andstraightening the holes in that portion of the laterally extendedportion which is to be left to form the tip platform or shroud.

Thus, for example, a blank can be extruded so as to form the normal rootand blade portions with axial holes running through the blade portion,and the end of the blade portion remote from the root can then be upsetto form an embryo shroud portion which is subsequently shaped byextrusion through a die or by means of a forging die. The extrusion dieor the forging die will have a cavity formed in it beyond the end of theblade and so located that material in the neighbourhood of the deflectedportions of the holes can flow into the cavity thus relieving the stressand drawing out the holes until a they are substantially straight inthat part of the metal which is to form the shroud.

Where there are two series of holes each series being on different sidesof the centre line of the blade crosssection the effect of the upsettingwill be to cause the series of holes to be bent so as to increase theamount of metal between them in the centre of the upset portion. Thecavity in the final extrusion die is so placed that this extra metal isdrawn out straightening out the holes at least in that portion of theupset part of the blank which is nearest to the blade proper and whichwill after ma chining form the tip shroud.

An example of this invention is illustrated in the accompanying drawingsin which:

FIGURE 1 is a side elevation of a blank with holes drilled in it;

FIGURE 2 is an end elevation of the same blank;

FIGURE 3 is a side elevation after extrusion; FIGURE 4 is an endelevation corresponding to FIG- URE 3;

FIGURE 5 is a side elevation after the upper end has been upset to forman embryo shroud or platform;

FIGURE 6 is a section on line 6--6 of FIGURE 5;

FIGURE 7 shows a further stage in forming the platfo htates Patent f) lc2,999,303 Patented Sept. 12, 1961 FIGURE 8 is a side elevation of theblade in the stage shown at FIGURE 7; and

FIGURE 9 is a side elevation of the finished blade.

Initially holes 10 are drilled in a blank 11 (FIGURES 1 and 2). Theholes may as shown be drilled completely through the blank or they maybe blind holes drilled only through the portion of the blade which is toform the blade and tip shroud, leaving the extension of the holesthrough the root portion to be drilled after extrusion.

The holes are then filled with a filler material which may be a lowcarbon steel. The blank 11 is then partially extruded to form a bladeportion 12 sufiiciently long to provide a potential shroud portion(FIGURES 3 and 4).

These extrusions take place in a split die and the pressure is from twosides of the blank only, that is to say from the top and bottom sides asviewed in FIGURES 2 and 4 so that the holes are progressively elongatedin cross section as shown in those figures.

The potential shroud portion is then electrically upset to produce theshape 13 shown at FIGURE 5 and this results in kinking of the holes asshown at 10a in FIG- URE 6.

The shroud, or platform, 13 is then forged between a split die 15 and asolid die 15a in which is a cavity 16 to receive metal 17 from theportion of the shroud 13 at the ends of the holes 19. The portion of theeX- trusion below the platform 13 is gripped between the parts of thesplit die 15.

Cavity 16 enables metal to flow and tends to straighten the holes 10 andat the same time to relieve stresses in the metal.

The part 17 can be used in subsequent machining operations for markingdatums on and for setting up on machines.

The blade is finally machined to the form in FIGURE 9 in which there isa root portion 14a, blade portion 12a and shroud portion 13a. It will beseen that the shroud portion 13a has only straight holes 10b in it.

The metal filler rods are removed at a stage after the last extrusionand/or forging process.

I claim:

1. The process of forming a platformed or shrouded blade for an internalcombustion turbine engine from a blank having a plurality oflongitudinal axially disposed holes extending through the potentialplatform end thereof and filled with a deformable material comprisingextruding said blank to provide a blade portion of relatively thinelongated cross-section, upsetting the said end into a laterally widenedplatform portion having an undersurface facing away from said end, saidplatform being of greater thickness than needed for the finished productthereby kinking the tilled holes to substantially follow the outline ofthe widened portion, further shaping the platform portion by engagingits under surface and forcing the platform in a die having a cavityshaped in plan to receive it and having a longitudinal extension cavityof approximately blade thickness and width thereby to extrude metal fromthe platform in the extension cavity thus drawing out and straighteningthe holes in that portion of the upset blade end which is left to formthe tip platform or shroud.

2. The process of claim 1 in which the upper portion of the extrudedplatform and extension are machined away and the hole fillers removed.

3. The process of forming a blade for an internal combastion turbinefrom a blank containing a plurality of longitudina wally-disposed holesextending through one end thereof and filled with a deformable material,said holes being in two series, each series being on a different side ofthe center line of the blade cross-section, comprising extruding saidblank to form a blade portion of relatively thin elongatedcross-section, upsetting the said end into a laterally widened platformportion having an undersurface facing away from said end and therebykinking the holes of each series oppositely to roughly follow theoutlines of widened portion, further shaping the platform by pressureapplied to its under surface to force it into a hollow die shaped tothereby thin the platform and having a longitudinal cavity ofapproximately blade thickness and width in alignment with the blade toreceive the 4 extruded metal thus drawing out and straightening theholes in the remaining platform portion whereby they are in substantialalignment with the holes in the blade portion.

References Cited in the file of this patent UNITED STATES PATENTS2,093,775 Colwell Sept. 21, 1937 2,743,509 Freedman May 1, 19562,759,257 Schlegel Aug. 21, 1956 2,891,307 Betteridge June 23, 1959FOREIGN PATENTS 726,909 Great Britain Mar. 23, 1955

